Stabilisation of continuous Z-purlins by sandwich panels: Full scale experimental approach

• The authors have observed the absence of code provisions for practical cases involving sandwich panel roofing supported by Z-purlins.
• A local investigation on the purlin–panel fastener behaviour has been conducted infirming the panel indentation effect under wind up-lift.
• A 1:1 scale experimental arrangement has been tested in the laboratory.
• The measurements performed have enabled to apply the simplified procedure in EN 1993-1-3 in a practical and more direct way.

The sandwich panel roof supported by continuously connected thin-walled cold-formed Z-purlins with overlapping over intermediate supports is a practical case of very frequent use. Among the two possible directions of investigation mentioned in the code when studying torsional/distortional instability of Z-purlins (i.e. rotational stiffness and linear stiffness) the authors have chosen to look at the notional linear spring placed at the free flange of the purlin. The linear spring is defined by EN 1993-1-3 Annex A5, as an equivalent or alternative to the stabilizing rotational spring generated by the continuous connection of the sandwich panels to purlin upper flange. This type of approach, on authors' opinion, has the advantage to include into the experimental phase, the real imperfections, and support conditions characteristic to such roof systems, having a very important impact on purlin stability behaviour. A description of the proposed full scale arrangement and experimental conditions, plus values of obtained results are given in the paper.